The Joy of Soldering: How to Get Started

Becoming a master of the melting, flexing, and gluing powers of solder can help you start building your own electronics.

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1The Basics

Matthew Woodson

For hobbyists who want to create their own electronics from scratch, there comes a time in every project when two metal surfaces must merge. Solder, which changes from a flexible solid to a liquid, then back to a solid in seconds, is the magical metal glue that makes this happen. Solder can also be a frustrating mess. For reasons both aesthetic and functional, you'll want to learn how to work with it cleanly and neatly, because sloppy soldering means your project might not work.

The best solder for electronics is 60 percent tin and 40 percent lead and filled with rosin, a pine-tree secretion that slows oxidation to help the metal flow.

2MEET THE MATERIALS

Matthew Woodson

Printed circuit boards (PCBs) connect together electronic components (capacitors, resistors, LEDs, microcontrollers, sockets, etc.). Solder gives those components structural and electrical footholds at the spots where they're mounted, called pads. It's important that these surfaces start out clean, so wipe the PCB with a nonabrasive scrubber.

3COMPONENT LEADS

Matthew Woodson

The wires sticking out of components are called leads. Some parts, such as microcontrollers, come with rigid leads that align with the pads on the PCB, and others, such as resistors, come with longer leads that bend to fit. Some parts have one lead, some two, some 28 or more.

4ADD COMPONENTS TO THE BOARD

Matthew Woodson

To connect a component to the board, push its leads through holes in the pads—only one lead goes into each pad—and bend them about 45 degrees to keep the component from falling out. Next, hold the iron like you would a pencil and press it against the pad and lead for 1 second. Then push about 1 to 3 mm of solder between the lead and the pad, where it will melt against the heated components. Hold the tip steady for another second or two so the solder has a chance to flow around the lead. It's key to heat the components themselves, not the solder directly, which can cause a cold joint; components that aren't hot enough won't bond to the solder properly, leaving the joint weak.

SAFETY TIP

Try not to let that metal flow onto your hands—not only is the solder hot, the lead is toxic. Wash your hands after soldering so you don't leave any residue on your skin.

5CHECK CONNECTIONS

Matthew Woodson

A perfect connection will look like a small bump around the lead and will completely cover the pad. If some of the pad is still exposed or the connection is flat, you haven't used enough solder, and you may end up with an incomplete connection. The fix is simply to add more solder, but not too much—that could create a connection where you don't want one, shorting the circuit and directing electricity down the wrong path.

6CUT THE LEAD

Matthew Woodson

The last step is trimming the leads. If they remain too long, they may bend and touch each other, potentially causing a short circuit. Using a wire cutter, snip each lead just above the mound of solder. Hold on to the end of the lead to ensure you don't get speared in the eye by flying wire.

7JOIN WIRE TO WIRE

Matthew Woodson

Solder is also great for fusing wires. Match each wire's gauge to the markings on a wire stripper and remove about 3 mm of insulation from its end.

8TIN THE ENDS

Matthew Woodson

Heat the exposed wires with the soldering iron and coat the ends with a thin layer of solder—a process called tinning—to ensure the wires form a proper connection. Then join the wires by pressing the iron to both wire tips, melting them together. Once the solder has melted, remove the iron and hold the wires still until the metal cools. Then you—and your wires—are set.

9CLEANING THE TIP

Matthew Woodson

Because a soldering iron heats to almost 400 F, the tip oxidizes quickly, creating solder rust that blocks the flow of heat. So before soldering each connection, use a wet sponge to clean the tip of the iron (it's clean when it shines) to remove any buildup.

10SUPPLIES

Dvenosa/Flickr

Soldering is an affordable art. You can set yourself up with a full tool kit for less than $30.

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